Ethanol Exposure Decreases Glutamate Uptake in the Nucleus Accumbens

Authors


Reprint requests: Roberto I. Melendez, PhD, Medical University of South Carolina, Department of Physiology and Neuroscience, 173 Ashley Avenue, Suite 403 BSB, Charleston, SC 29425; Fax: 843-792-4423; E-mail: melendez@musc.edu

Abstract

Background:

An increased level of extracellular glutamate is a key neurochemical feature associated with ethanol exposure and withdrawal.

Methods:

In the current study, extracellular levels of glutamate and glutamate transport in the nucleus accumbens were assayed 24 hr after repeated ethanol exposure (1 g/kg ip daily for 7 days) with use of in vivo no-net-flux microdialysis and in vitro 3Hglutamate uptake, respectively.

Results:

Microdialysis revealed higher extracellular glutamate concentrations in the nucleus accumbens of rats that were given ethanol. The increase in basal extracellular glutamate levels was accounted for in part by a decrease in the in vivo probe recovery of glutamate. Moreover, an in vitro accumbens slice preparation measuring 3Hglutamate uptake revealed that Na+-dependent 3Hglutamate uptake was significantly reduced 24 hr after 7 days of repeated ethanol exposure. The ethanol-induced deficit in glutamate uptake was not associated with decreased total tissue levels of the transporters GLAST or GLT1. The in vivo and in vitro ethanol-induced changes in glutamate levels and uptake returned to control levels 14 days after discontinuing 7 days of repeated ethanol exposure.

Conclusions:

These results suggest that the previously reported increases in extracellular glutamate induced by ethanol exposure may be due in part to deficits in glutamate transport.

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